// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_MAC_SCOPED_OBJC_CLASS_SWIZZLER_H_
#define BASE_MAC_SCOPED_OBJC_CLASS_SWIZZLER_H_

#import <objc/runtime.h>

#include "base/base_export.h"
#include "base/macros.h"

namespace base {
namespace mac {

    // Within a given scope, swaps method implementations of a class interface, or
    // between two class interfaces. The argument and return types must match.
    class BASE_EXPORT ScopedObjCClassSwizzler {
    public:
        // Given two classes that each respond to |selector|, swap the implementations
        // of those methods.
        ScopedObjCClassSwizzler(Class target, Class source, SEL selector);

        // Given two selectors on the same class interface, |target| (e.g. via
        // inheritance or categories), swap the implementations of methods |original|
        // and |alternate|.
        ScopedObjCClassSwizzler(Class target, SEL original, SEL alternate);

        ~ScopedObjCClassSwizzler();

        // Return a callable function pointer for the replaced method. To call this
        // from the replacing function, the first two arguments should be |self| and
        // |_cmd|. These are followed by the (variadic) method arguments.
        IMP GetOriginalImplementation();

    private:
        // Delegated constructor.
        void Init(Class target, Class source, SEL original, SEL alternate);

        Method old_selector_impl_;
        Method new_selector_impl_;

        DISALLOW_COPY_AND_ASSIGN(ScopedObjCClassSwizzler);
    };

} // namespace mac
} // namespace base

#endif // BASE_MAC_SCOPED_OBJC_CLASS_SWIZZLER_H_
